Installing on-board sensor beams at the neutral axis of bending of a load bearing member such as a truck drive axle or front axle is disclosed by the U.S. Pat. No. 5,327,791 to Walker, 1992.
The prior art design, with four (4) mounting points, secures a “dog bone” shaped sensor beam sufficiently enough to force it to bend with the load bearing structure. Its neutral axis corresponds to that of the load bearing structure and follows its arc of bending.
Although very useful in the truck scale industry this technique has limitations. Its size limits its utility. For example: current 12 inch long beams must straddle spring attachment U-bolts to find a suitable installation location. This spacing away from the drive axle housing necessitates tall weld brackets (up to 1¼ inches). There is a need for a new design that would reduce the size (length) of sensor beam to increase utility. An 8 inch long sensor beam would install inboard of U-bolts and outboard of the drive axle banjo.
Its relatively low output signal limits noise reject and hinders weight resolution. There is a need to increase the output signal of the sensor beam by some mechanical amplification technique. Simply shortening a beam significantly reduces its output signal. However, making a sensor beam longer would increase its output signal but would also further limit its utility.
There is a need to review hardware being used in sensor beam installation to improve proximity of the sensor to the load bearing member. There is a further need to reduce shear and bending forces on mounting bolts or studs to improve linearity and zero return of installed sensors.
The aforementioned arc approximates a circular function for the center section of a front axle between the spring mounts. The arc of bending for a drive axle is exponential in character, i.e., deflection increases an amount that is more than proportionate to the distance from the drive axle centerline as that distance increases. In both of the above situations, the deflection available to drive the sensor is only 0.005 inches for prior art sensor beams. It is even less for shorter sensor beams. Because existing neutral axis sensor beams reside in a low deflection zone with respect to load bearing members, there is a need for some multiplying or amplifying factor to facilitate a new design.